Aerosol Index

Aerosol Index

Aerosols absorb and scatter incoming sunlight, which reduces visibility and increases the optical depth. Aerosols have an effect on human health, weather and the climate. Sources of aerosols include pollution from factories, smoke from fires, dust from dust storms, sea salts, and volcanic ash and smog. Aerosols compromise human health when inhaled by people with asthma or other respiratory illnesses. Aerosols also have an affect on the weather and climate by cooling or warming the earth, helping or preventing clouds from forming.

Satellite-derived Aerosol Index products are useful for identifying and tracking the long-range transport of volcanic ash from volcanic eruptions, smoke from wildfires or biomass burning events and dust from desert dust storms, even tracking over clouds and areas of snow and ice.

The Ozone Mapping and Profiler Suite (OMPS) AI indicates the presence of UV-absorbing particles in the air (aerosols) such as desert dust and soot particles in the atmosphere. The unitless range of the AI is from 0.00 to >=5.00, where 5.0 indicates heavy concentrations of aerosols that could reduce visibility or impact human health and this satisfies the needs of most users. However, the AI signal for pyrocumulonimbus (pyroCb) events, which are both dense and high in the atmosphere, can be much larger than 5.0. To provide better near real-time imagery for these high AI events, the pyroCb product with an upper AI limit of 50.0. The sensor resolution is 50 km, imagery resolution is 2 km, and the temporal resolution is daily. L2 Sulfur Dioxide (SO2) Total Column Swath 13x24 km

Aerosol Optical Depth

Aerosol Optical Depth

Aerosol Optical Depth (AOD) (or Aerosol Optical Thickness) indicates the level at which particles in the air (aerosols) prevent light from traveling through the atmosphere. Aerosols scatter and absorb incoming sunlight, which reduces visibility. From an observer on the ground, an AOD of less than 0.1 is “clean” - characteristic of clear blue sky, bright sun and maximum visibility. As AOD increases to 0.5, 1.0, and greater than 3.0, aerosols become so dense that sun is obscured. Sources of aerosols include pollution from factories, smoke from fires, dust from dust storms, sea salt, and volcanic ash and smog. Aerosols compromise human health when inhaled by people, particularly those with asthma or other respiratory illnesses. Aerosols also have an effect on the weather and climate by cooling or warming the earth, helping or preventing clouds from forming. Since aerosols are difficult to identify when they occur over different types of land surfaces and ocean surfaces, Worldview provides several different types of imagery layers to assist in the identification.

Carbon Monoxide

Carbon Monoxide

Carbon Monoxide (CO) is a poisonous, odorless and colorless gas. CO is produced by incomplete combustion of fossil fuels and biomass burning. It is one of the longest-lived, naturally occurring atmospheric carbon compounds. CO is a trace gas produced by methane oxidation, fossil fuel consumption (emitted from factories and cars) and biomass burning (from forest fires and agricultural burning). These measurements are useful for analyzing the distribution, transport, sources and sinks of CO in the troposphere and can be used to observe how it interacts with land and ocean biospheres. CO hinders the atmosphere’s natural ability to rid itself of harmful pollutants.

The Atmospheric Infrared Sounder (AIRS) Carbon Monoxide (CO) Total Column (Day/Night) layer indicates the amount of Carbon Monoxide (CO) in the total vertical column profile of the atmosphere (from Earth’s surface to top-of-atmosphere) and is measured in parts per billion by volume (ppbv).The imagery resolution is 2 km and sensor resolution is 45 km. L2 standard retrieval product using AIRS IR only

The Measurements of Pollution in the Troposphere (MOPITT) Carbon Monoxide (Level 2, Daily, Day/Night, Total Column) layer shows the amount of carbon monoxide (CO) present in the total vertical column of the lower atmosphere (troposphere) and is measured in mole per square centimeter (mol/cm2) for the Day and Night overpasses, in near real-time (NRT). MOPITT NRT measurements use thermal-infrared radiation at 4.7 µm to produce CO total column abundance. MOPITT NRT Level 2 CO vertical profiles derived from Thermal Infrared Radiances.

Corrected Reflectance Imagery

Corrected Reflectance Imagery

Moderate Resolution Imaging Spectroradiometer (MODIS) and VIIRS Corrected Reflectance imagery are available only as near real-time imagery. The imagery can be visualized in Worldview and Global Imagery Browse Services (GIBS). More:

Fire

Fire

The VIIRS and MODIS Fire and Thermal Anomalies layer shows active fire detections and thermal anomalies, such as volcanoes, and gas flares. Fires can be set naturally, such as by lightning, or by humans, whether intentionally or accidentally. Fire is often thought of as a menace and detriment to life, but in some ecosystems it is necessary to maintain the equilibrium, for example, some plants only release seeds under high temperatures that can only be achieved by fire, fires can also clear undergrowth and brush to help restore forests to good health, humans use fire in slash and burn agriculture, to clear away last year’s crop stubble and provide nutrients for the soil and to clear areas for pasture. The fire layer is useful for studying the spatial and temporal distribution of fire, to locate persistent hot spots such as volcanoes and gas flares, to locate the source of air pollution from smoke that may have adverse human health impacts.

The MODIS Fire and Thermal Anomalies product is available from the Terra (MOD14) and Aqua (MYD14) satellites as well as a combined Terra and Aqua (MCD14) satellite product. The thermal anomalies are represented as red points (approximate center of a 1 km pixel) in Worldview/GIBS.

The VIIRS 375m I-band fire detections complements the MODIS fire detections; they both show good agreement in hotspot detection but the improved spatial resolution of the 375m data provides a greater response over fires of relatively small areas and provides improved mapping of large fire perimeters. The 375m data also has improved nighttime performance. Consequently, these data are well suited for use in support of fire management (e.g., near real-time alert systems), as well as other science applications requiring improved fire mapping fidelity.The thermal anomalies are represented as red points (approximate center of a 375 m pixel). VIIRS/Suomi NPP Active Fires L2 Swath 375m

In comparison with the MODIS Corrected Reflectance product, the MODIS Land Atmospherically Corrected Surface Reflectance product (MOD09) is a more complete atmospheric correction algorithm that includes aerosol correction, and is designed to derive land surface properties.

VIIRS Land Surface ReflectanceThe VIIRS Surface Reflectance provides continuity with the EOS-MODIS Land Surface Reflectance product.The Suomi NPP/VIIRS surface reflectance products are estimates of surface reflectance in each of the VIIRS reflective bands I1-I3, M1-M5, M7, M8, M10, and M11. Surface reflectance for each moderate-resolution (750m) or imagery-resolution (375m) pixel is retrieved separately for the Level-2 products and is obtained by adjusting top-of-atmosphere reflectance to compensate for atmospheric effects. Corrections are made for the effects of molecular gases, including ozone and water vapor, and for the effects of atmospheric aerosols. The inputs to the surface reflectance algorithm include top-of-atmosphere reflectance for the VIIRS visible bands (VNP02MOD, VNP02IMG), the VIIRS cloud mask and aerosol product (NPP-CMIP_L2), aerosol optical thickness (NPP_VAOTIP_L2, NPP_VAMIP_L2), and atmospheric data obtained from a reanalysis (surface pressure, atmospheric precipitable water, and ozone concentration). All surface reflectance products are produced for daytime conditions only.

In mid-August 2018, deadly blazes across the western United States and Canada created thick plumes of smoke.The VIIRS instrument on the joint NASA/NOAA Suomi NPP satellite acquired this image (top) on August 15, 2018. Smoke is seen hovering over much of western North America and central Canada. Read more at NASA's Earth Observatory.